First off, grab yerself a bakin' sheet and line it with some trusty ol' aluminum foil. Lay them big ol' poblano peppers on that sheet. Now, pop that sheet right on the tippy-top rack of yer oven and set it to broil on high. Let 'em cook for 'bout 15 minutes, flippin' 'em every 5 minutes to make sure they get a nice roastin'.
Once them peppers have had their time in the oven, take 'em out and toss 'em into a sealable plastic bag. Let 'em sit there for 'bout 10 minutes so they can steam and get all tender.
While them peppers are doin' their steamin' thang, go ahead and preheat yer oven to a toasty 375°F.
Now, let's whip up that tasty sauce. Grab yerself a trusty ol' saucepan and toss in all them sauce ingredients. Slowly bring it all to a nice, gentle boil.
Once it's all boiled up, transfer the sauce to a food processor and give it 'bout 10 pulses. We wanna smooth it out a bit, but still keep a few chunky bits of them veggies.
Grab yerself a good ol' cast-iron skillet or an oven-safe pan/dish. Pour 'bout two-thirds of that yummy sauce into the bottom of the pan.
Take them steamed peppers out of the plastic bag, make a little slit on the side, and remove them seeds and stem. Flip 'em over and peel off as much of that charred skin as you can manage. Be careful now, 'cause them peppers are still mighty hot!
Now, flip them peppers back over and stuff 'em full of a whole mess of cheese. I like mixin' it up with some queso fresco, sharp cheddar, and mozzarella. Get it all nice and cozy in there.
Roll up them sides of the pepper and gently place 'em, open side down, in the pan with the sauce. Don't fret if they tear a bit; we'll cover 'em up with more sauce and cheese soon enough.
Time to cover them cheese-stuffed peppers with the rest of that sauce and sprinkle on some more of that gooey, melty cheese.
Pop that pan right into the preheated oven at 375°F and let 'em bake for 'bout 25 minutes. Once they're all nice and bubbly, take the pan out of the oven.
Now comes the fun part! Serve them delectable rellenos with a sprinkle of chopped green onion, some creamy avocado slices, and a dollop of sour cream on top. Y'all ready to dig in? Enjoy every scrumptious bite, sugar!